An endoscope is a surgical tool designed to be placed inside a body in order to provide a view of the portion of the body in which it is inserted. In endoscopic surgery, an endoscope is placed in a body at the location at which it is necessary to perform a surgical procedure. Other surgical instruments are placed in the body at the surgical site. The surgeon views the surgical site through the endoscope in order manipulate the other surgical instruments to perform the desired surgical procedure. The development of endoscopes and their companion surgical instruments has made it possible to perform minimally invasive surgery that eliminates the need to make a large incision to gain access to the surgical site. Instead, during endoscopic surgery, small openings, called portals, are formed. One advantage of performing endoscopic surgery is that since the portions of the body that are cut are reduced, the portions of the body that need to heal after the surgery are likewise reduced. Still another advantage of endoscopic surgery is that it exposes less of the interior tissue of the patient's body to the open environment. This minimal opening of the patient's body lessens the extent to which the patient's internal tissue and organs are open to infection.
The ability to perform endoscopic surgery is enhanced by the availability of light sources designed to illuminate the surgical site inside the patient. A typical light source includes a light-emitting bulb that is located outside of the patient in a control console. A fiber optic cable extends between the control console and the endoscope. The cable has a proximal end that is adapted to receive the light emitted by the bulb and a distal end that is coupled to a complementary light post integral with the endoscope. (Hereinafter it shall be understood that “proximal” means towards the light source and “distal” means towards the end of the endoscope positioned at the surgical site.) When the light source is energized, the light emitted by the bulb is transmitted through the cable to the endoscope. A set of optical fibers in the endoscope transmit the light to the surgical site. The emitted light illuminates the surgical site so as to make it easier for surgical personnel to observe the site.
While current light sources have facilitated the advancement of endoscopic surgery, they are not without disadvantages. One particular disadvantage relates to the fact that, in order to illuminate a surgical site, the light source for an endoscopic is required to transmit a large amount of light energy. For example, some of these light sources include light emitting bulbs that is supplied with 250 Watts, have luminous intensity of approximately 2,500 candelas, and an average luminance of 40,000 cd/cm2. Problems arise with these light sources because, during endoscopic surgery, it may be necessary to switch the endoscope that is used on a patient. A change of endoscope may be necessary if, during the surgical procedure, a different field of view of the surgical site is desired; such change in perspective can sometimes only be obtained by switching endoscopes. During this switch of the endoscopes, the distal end of the fiber optical cable is disconnected from the first endoscope and coupled to the second endoscope. Prior to the fiber optic cable being attached to the second endoscope, it is often momentarily placed on a surgical drape. A problem can occur because the light energy emitted by the fiber optic cable can rapidly warm the surface on which the distal end of the cable is placed. If the surface is cloth or paper, such as a surgical drape, there is a potential that this energy may singe the drape. If the fiber optic cable is inadvertently left on the drape for an extended period of time, the heat generated could potentially cause the drape to either burn or ignite.
Moreover, another problem associated with illuminating the surgical site during an endoscopic surgical procedure is that the light directed towards the site invariably changes during the course of the procedure. This change occurs because the endoscope is subjected to both deliberate and involuntary movement during the course of a procedure. When, as a result of this movement, the distal end of the endoscope is moved towards the surgical site, the light it emits focuses on a relatively small surface. If the quantity of received light becomes relatively high, the view of the site is lost due to white-out. If the distal end of the endoscope is moved away from the surgical site, the light emitted diffuses over a relatively large surface. If the amount of light per unit surface area appreciably diminishes, the view of the site significantly darkens. In either situation, the surgeon's view of the surgical site may decay to the point at which it the ability to perform the surgical procedure is hampered. Moreover, even minor changes in the light present at the surgical field may be distracting.
In order to adjust for the problems associated with the changing quantities of light received per unit surface area at a surgical site, many currently available light sources are provided with feedback circuits. These circuits receive an indication of the amount of light that is reflected from the tissue surgical site. This indication typically comes from a camera mounted to the endoscope. Primary, the camera is a transducer that captures the images present at the surgical site in order to facilitate the display and recording of those images. The camera supplies signals representative of light intensity to a feedback circuit internal to the light source. Based on these input signals, the feedback circuit selectively adjusts the amount of the light emitted by the light source. This regulation ensures that the light present at the surgical site remains at a level that ensures the site can be properly viewed.
While the above feedback circuits work reasonably well, there are some limitations associated with current light sources. Specifically, the rate at which feedback adjustments the light emitted by endoscopes occur is a function of the type of endoscope. Often, during a surgical procedure, a surgeon will change the endoscope with which he/she views the surgical site. Presently, each time this change is made, surgical personnel must also manually input commands to the light source or camera in order to provide an indication of the new type of endoscope to which these components are connected. Requiring surgical personnel to perform this procedure can increase the time it takes for the overall surgical task to be accomplished. Moreover, since this procedure is performed manually, there is always the possibility that this procedure will either not be performed, or performed incorrectly. In either situation, until the light source feedback circuit receives a correct indication of the type of endoscope to which the light source is connected, the source may output light that is inappropriate for the endoscope with which it is used.